Magnetic high intensity arc



April 26, 1938. J. E. MCAULEY 2,115,688

MAGNETIC HIGH INTENSITY ARC Filed June 12, 1935 H/s ATTRNEY.

Patented Apr. 26, 1938 MAGNETIC HIGH INTENSITY ARC John E. McAuley, Chicago, Ill., assigner to J. E. McAuley Mfg. Co., Chicago, Ill., a. corporation of Delaware Application June 12, 1935, Serial No. 26,117

3 Claims.

This invention relates to high intensity flaming arc lights and to methods of producing the same.

The term high intensity arc is now used in the' art to designate a type of flaming arc in which l the intrinsic brilliancy of the flame, especially in the vicinity of the positive crater, greatly exceeds the intrinsic brilliancy of either the ordinary flaming arc or that of the pure carbon arc.

Atypical high intensity arc isy shown in the prior patents of Elmer A. Sperry, No. 1,227,210, dated May 22, 1917, and No. 1,357,827, dated lNovember 2, 1920. To produce such an arc not only requires the proper current and current density, but in the usual high intensity arc of the prior art, required positioning of the negative electrode at an angle tothe positive electrode and the rotation of the latter.

Further refinements in the manufacture of the -carbons themselves have enabled arc light users to obtain a high intensity effect at moderately low currents by employing small diameter cord electrodes, so that the current density remains high. For example, high intensity effects have been obtained with a positive electrode of 1A inch diameter or less, with currents of 32 amperes upwards, even with the electrodes substantially in l vline and non-rotating. Such an arc, however, has proved unsatisfactory for searchlight, picture projector and spot light purposes, since it is unstable and the intensity thereof may vary over one hundred per cent within a short time,

-By my invention, I have provided a simple means for rendering this type of arc stable and efllcient so that a brilliant, uniformly intense 35 flame is produced and maintained at the positive crater by a steady, upward pressure of the negative flame produced by causing the arc flames to emerge in a uniform upward direction. I secure this result by creating across the varc a 40 unidirectional magnetic field, as distinct from the fleld caused by the current flowing through the electrodes, preferably by a magnet located in such a position as not to cast a shadow or interfere with the light projected by the reflector. llref'erably, I locate the magnet to the rear of the mirror or reflector. I am aware that electric and magnetic fields have heretofore been created at the arc, but such fields are usually for the purpose of centralizing the arc by a l 'powerful uniform field produced by a heavy cur- .rent conductor close to the arc, but in my invention a very weak magnetic field is produced transverse to the arc to decentralize lthe arc flames by a magnet lentirely out of the projected Referring to the drawing showing my invention diagrammatically, Fig. l is a side elevation, partly -in section, of

a portion of a projector lamp such as used in,

motion pictures, with my invention applied thereto.

Fig. 2 is a similar view of 'the electrodes on a somewhat larger scale, showing clearly the preferred type of burning condition.

Figs. 3, 4 and 5 show the various types of burning conditions which the arcassumes, as operated in the prior art.

Fig. 6 is a face view of the magnet which is utilized in my preferred form to produce the magnetic field, as viewed from the left in Fig. 1.

As above stated, it is known that a high intensity effect may be produced at moderate currents with small, copper coated electrodes I and 2, the positive electrode being provided with a core 3 of flaming arc material and the negative electrode being provided with a smaller core 4 of arc supporting material. A transitory arc having some of the properties of a. true high intensity arc may be produced with such an arrangement by employing a short arc length, the arc then having the appearance shown in Fig. 4. Under this condition thehigh intensity fla-me 5 mushrooms out from the positive crater, presenting a more or less flattened forward surface 6, the negative flame directly impinging and spreading the positive flame in all directions. Any slight misalignment or defect in the shell of the positive electrode causes, under these conditions, a preponderance of the flame to issue at one side, resulting in a quick` burning through of the crater wall at that point and a burst of flame, followed by a loss of the desirable, symmetrica] deep crater and the high intensity effect. In other words, such an are does not persist, but flashes over to the burning conditions shown in Fig. 3 and to the burning conditions shown in Fig. 5, so that this arc is quite unsatisfactory as a source of light for motion pictures.

In Fig. 3 substantially no high intensity effect is obtained, no blue-white positive crater flame being visible in the arc as viewed from the side, and under these conditions the candle power of the light falls to less than half the candle power of Fig. 4. This arc may flash over to the condition shown'in Fig. 5, in which there is a burst of flame 5 from the positive crater in great volume, which almost touches the lnegative electrode. 'This does not persist, however, and the arc soon lapses back into either the form of Fig. 4 or the form of Fig. 3.

According to my invention, I place near the arc and preferably behind the reflector 1, some means for producing a magnetic field at the arc of the proper direction and magnitude to weaken the total flux eld above the arc as compared to the total iiux field below the arc, thereby pro- ,ducing a moderate upward deiiecting effect on the arc flame, causing the flame to emerge from the crater uniformly and at the same point. If at the same time the negative electrode, while being maintained parallel to the positive, is positioned so that the lower` portion of the positive crater is oxidized by the rising air currents as fast as the upper portion is burned away by the upwardly directed positive flame, a uniform; deep crater is maintained and a high intensity arc, as shown in Figs. 1 and 2, is produced and uniformly maintained without rotatingithe positive electrode land without inclining the negative. Preferably the axis of the negative is operated, for this purpose, slightly below the axis of the positive electrode. To this end, I have shown a permanent magnet 8 placed behind the reflector 1 with its poles in the proper position with respect to the direction of current flowing through the arc to produce the above described deflecting and steadying field. Preferably the two poles of the magnet lie above the electrodes, as shown in Figs. l and 6, whereby the main field produced thereby is above the electrodes and in opposition to the eld produced by the arc current flowing through the electrodes. By this means a steady high intensity arc is produced with the brilliant positive flame 5 pressed close to the positive crater, but deflected slightly upwardly. so that it does not bulge out evenly in all directions, but emerges mainly at the top. By this means a stable form of arc is produced which makes a steady, brilliant source of light, of great intrinsic brilliancy and suitable for use in either projector lamps or searchlights.

It is obvious that the magnetic field may be produced by different positions of the magnet or by different means. Fig. 2 illustrates the magnet 8' as in a horizontal position. back of the refiector 'l instead of in a vertical position, as shown in Figs. 1 and 6. Other means of producing a proper magnetic field through electromagnets or solenoids, or otherwise, will be readily apparent,

but I prefer that whatever means be employed be located outside of the beam of the projector,

As many changes could be made in the above construction and many; apparently widely difierent embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained inthe above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

Having described my invention, what I claim and desire to secure by Letters Patent is:

1. In a high intensity, moderate current projector lamp having a reflector, a non-rotating positive flaming arc electrode of relatively small diameter and having a shell and a core, a negative electrode having its axis substantially parallel thereto but slightly below the axis of the positive electrode, said electrodes being adapted to operate at short are length, and a magnet located outside of the beam from said reflector to weaken the total flux field above the arc as compared to the flux eld below the arc, whereby an upward defiecting effect is produced on the arc flames and a uniform deep crater is maintained by balancing the rate of the shell consumption.

2. A high intensity, moderate current projector lamp as claimed in claim 1, wherein the magnet is located behind the reflector and has both poles substantially above the electrodes for the purpose specified.

3. The method of producing a high intensity flaming arcwith moderate currents, and without either rotation of the positive electrode or angularly positioning the negative electrode, Which consists in employing a small positive electrode having a shell and a core whereby it is operated at high current density thereby producing distinct positive and negative flames, preventing the mushrooming of the former by the latter by decreasing the normal magnetic field intensity above the arc as compared to the magnetic eld intensity below the arc to produce an upward defiecting effect on the arc flames and balancing the shell consumption to maintain a uniform crater, by lowering the axis of the negative electrode.

JOHN E. MCAULEY.

Cil 

